622 EIGHTH PACIFIC SCIENCE CONGRESS 



The observation of mean sea level at Hachijo-sima has been con- 

 tinued since May 1951. Figure 9 shows the results from September 1951 

 to September 1952, with the values of Kushimoto, Ito and Mera Tidal 

 Stations (Central Meteorological Observatory). The position of the 

 tidal stations is shown in Figure 10. 



(i) The range of variation of mean sea level at Hachijo-sima was 

 very large compared with other tidal station. While the differences 

 between maximum and minimum were about 50 cm. at other stations, 

 the difference at Hachijo-sima reached to 140 cm. This was caused 

 by the translation of the Kuroshio. To demonstrate this we shall com- 

 pare the variation of sea level with the oceanographic observations car- 

 ried out in the same period. The water level at Hachijo-sima was be- 

 tween 250 cm. and 260 cm. until September 1951. Then it lowered 

 greatly from the middle of October and from November 1951 to April 

 1952 (December 1951-February 1952 observation lacked) it remained 

 between 170 and 220 cm. At the beginning of May, it rose suddenly 

 about 50 cm. and then continued to rise slowly until September 1952- 

 According to the oceanographic observations, in May -August 1951, the 

 Kuroshio was obviously to the north of Hachijo-sima, in September-De- 

 cember, as there was no observation, the condition was not clear, but 

 from the Ten-day Marine Report of the Central Meteorological Obser 

 vatory, there appeared a cold water mass in this area. In February 1952 

 a cold water mass was situated in Enshu-nada and the Kuroshio run 

 around this and Hachijo-sima was situated at the north boundary of 

 the Kuroshio (Fig. 5). In April the Kuroshio was flowing near Miyake 

 sima. These facts were well coincided with the variation of sea level, 

 and we can conclude that by the observation of sea level, it is possible 

 to pursue the translation of the Kuroshio. 



The slope of sea surface at the strong current of the Kuroshio can 

 be assumed to be about 10-15 cm/ 10 miles. Therefore, that the sharp 

 rise of the sea level at the beginning of May was a rate of about 10 

 cm/day, indicated that the velocity of translation of the Kuroshio was 

 5-10 miles/day, namely 0.2-0.4 knots. 



This cold water mass was much smaller in scale and continued in 

 shorter time than the one mentioned in the preceding paragraph, h 

 is interesting to note that before the appearance of this cold water mass 

 a strong typhoon, Ruth, had swept over our country on 15 October. 



(ii) It was made dear that the variation of mean sea level at Ha 

 chijo-sima had close connection with the translation of the Kuroshio 

 The most interesting point in the variation is that there appear some 

 remarkable periodic changes and this may indicate that there are cor- 

 responding meanderings of the Kuroshio. 



